COLUMBIA, Mo. (AP) -- Experts on hiring in higher education say the University of Missouri could have a difficult time replacing out-going president Elson Floyd. Floyd announced last week he was leaving his job as system president to run Washington State University. Claire Van Ummerson of the American Council on Education says there is a very limited pool of candidates for top levels in administration. Van Ummerson says that creates tremendous competition for the best ones. North Dakota's university system recently extended its deadline for chancellor applications after receiving only three. Other schools looking for top administrators include Ohio State, Iowa, Indiana, Purdue and New Mexico. Experts say retiring administrators is partly to blame for the buyer's market. According to the Association of American Universities, 40 percent of current presidents at its members chool will soon retire. The University of Missouri-Columbia is a member of the association.